Separated Primers in AR-15s

There's a reason that military brass usually has crimped-in primers. That reason, is that a primer floating around inside of your AR-15's action can immediately bring your rifle to a screeching halt.

In my case, the primer popped out of the round as it was being chambered, then fell down below into the fire control group. When I pulled the trigger, nothing happened. I ejected the round, at which point I got to see the "salt and pepper shaker" display of the powder pouring out of the empty flash hole on the round. I ejected the round, blew out the powder, then chambered another.

I pulled the trigger, and there was a pop as I was pulling it. That was the primer getting crushed by the trigger, then detonating. The action siezed up, and I thought I had a hangfire. I left the weapon alone for 30 seconds, then when I returned, I noticed the trigger was firmly stuck and wouldn't travel forwards or backwards. So, I pushed out the takedown pins and separated the upper and lower.

Looking inside, the lower, I was able to notice the mangled body of the primer from the round which had lost its primer. In the picture below, you should be able to notice it - it's the yellow dot on the left side of the trigger assembly. The primer could not be extracted at the range, because I hadn't brought a pick to dig it out with. Which is just as well, because it gave me an opportunity to take these pictures. Now that I think of it, a spare firing pin would have been a good field-expedient way to remove the stuck primer.

At any rate, this loose primer demonstrates why the US military insists that all of its rounds have crimped-in primers. A single primer getting loose could easily cost a soldier's life in a firefight!

It's worth knowing that DPMS now has a widget called the "Receiver Rug", designed to combat this specific issue. DPMS thoughtfully sent me a review sample, and based on my thorough but by no means exhaustive testing, I can say I would be surprised if this jam could still happen on a rifle fitted with their product.

The primer, wedged underneath the trigger and preventing it from travelling